Noise detecting circuit and associated system and method

ABSTRACT

A noise detecting circuit including an amplifier circuit, a filtering circuit and a comparing circuit. The amplifier circuit is arranged to amplify an input signal and output an amplified signal, wherein the input signal is received from a circuit to be detected and indicates a noise level of the circuit to be detected. The filtering circuit is coupled to the amplifier circuit and arranged to filter the amplified signal and output a filtered signal. The comparing circuit is coupled to the filtering circuit and arranged to compare the filtered signal to a reference voltage and output an output signal indicating the noise level of the circuit to be detected.

BACKGROUND

In some platforms such like a Wafer Acceptance Test (WAT) platform, theintegrated circuit (IC) testing is difficult because the testingequipment limitation or the requirement of some specific devices.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a diagram illustrating a noise detecting system in accordancewith an embodiment of the present disclosure.

FIG. 2 is a diagram illustrating an amplifier circuit in accordance withan embodiment of the present disclosure.

FIG. 3 is a diagram illustrating an OTA in accordance with an embodimentof the present disclosure.

FIGS. 4A and 4B are diagrams illustrating configurations of an amplifiercircuit for detecting the noise level of an OTA in accordance with anembodiment of the present disclosure.

FIG. 5 is a diagram illustrating configurations of an amplifier circuitfor detecting the circuit to be detected coupled to the amplifiercircuit in accordance with an embodiment of the present disclosure.

FIG. 6 is a diagram illustrating a filtering circuit in accordance withan embodiment of the present disclosure.

FIG. 7 is a diagram illustrating a calibration mechanism for a resistorand a capacitor in accordance with an embodiment of the presentdisclosure.

FIG. 8 is a diagram illustrating a comparing circuit in accordance withan embodiment of the present disclosure.

FIG. 9 is a diagram illustrating the noise after each circuit in a noisedetecting circuit in accordance with an embodiment of the presentdisclosure.

FIG. 10 is a diagram illustrating operations of an analyze device inaccordance with an embodiment of the present disclosure.

FIG. 11 is a flowchart illustrating a first part of a noise detectingmethod in accordance with an embodiment of the present disclosure.

FIG. 12 is a flowchart illustrating a second part of a noise detectingmethod in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the disclosure.Specific examples of components and arrangements are described below tosimplify the present disclosure. These are, of course, merely examplesand are not intended to be limiting. For example, the formation of afirst feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath.” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the disclosure are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard deviation found in therespective testing measurements. Also, as used herein, the term “about”generally means within 10%, 5%, 1%, or 0.5% of a given value or range.Alternatively, the term “about” means within an acceptable standarderror of the mean when considered by one of ordinary skill in the art.Other than in the operating/working examples, or unless otherwiseexpressly specified, all of the numerical ranges, amounts, values andpercentages such as those for quantities of materials, durations oftimes, temperatures, operating conditions, ratios of amounts, and thelikes thereof disclosed herein should be understood as modified in allinstances by the term “about.” Accordingly, unless indicated to thecontrary, the numerical parameters set forth in the present disclosureand attached claims are approximations that can vary as desired. At thevery least, each numerical parameter should at least be construed inlight of the number of reported significant digits and by applyingordinary rounding techniques. Ranges can be expressed herein as from oneendpoint to another endpoint or between two endpoints. All rangesdisclosed herein are inclusive of the endpoints, unless specifiedotherwise.

In some scenarios, the integrated circuit (IC) testing is difficultbecause the testing equipment limitation or the requirement of somespecific devices. For example, in a Wafer Acceptance Test (WAT)platform, the frequency of the clock signal is limited to 10 MHz, andusing the spectrum analyzer is forbidden. In addition, a specific GSGprobe card is required. Therefore, in order to learn the noise level ofthe circuit/device in the WAT platform, too many obstacles need to beovercome. Accordingly, this present disclosure proposes a noisedetecting circuit, a noise detecting system and a noise detecting methodto at least solve the aforementioned problem.

FIG. 1 is a diagram illustrating a noise detecting system 1 inaccordance with an embodiment of the present disclosure. In someembodiments of the present disclosure, the noise detecting system 1includes a noise detecting circuit 10 including an amplifier circuit 11,a filtering circuit 12 and a comparing circuit 13. In some embodimentsof the present disclosure, a circuit to be detected is coupled to thenoise detecting circuit 10, and the noise detecting system 1 is arrangedto detect the noise level of the circuit to be detected. In someembodiments of the present disclosure, the noise detecting system 1 isarranged to detect the noise level of an operational transconductanceamplifier (OTA) 111 (shown in FIG. 2) of the amplifier circuit 11.

The amplifier circuit 11 receives an input signal IN and outputs anamplified signal AS. In some embodiments of the present disclosure, theamplifier circuit 11 is arranged to output the amplified signal AS byamplifying the input signal IN with a predetermined gain. In someembodiments of the present disclosure, the input signal IN is receivedfrom a circuit to be detected which will be discussed later. In someembodiments of the present disclosure, the input signal IN indicates anoise level of the circuit to be detected.

The filtering circuit 12 receives the amplified signal AS and outputs afiltered signal FS. In some embodiments of the present disclosure, thefiltering circuit 12 is arranged to output the filtered signal FS byfiltering the amplified signal AS with a predetermined corner frequency.The comparing circuit 12 receives the filtered signal FS and outputs anoutput signal OS. In some embodiments of the present disclosure, thecomparing circuit 13 is arranged to output the output signal OS bycomparing the filtered signal FS to a reference voltage. In someembodiments of the present disclosure, the output signal OS indicatesthe noise level of the circuit to be detected.

In some embodiments of the present disclosure, the noise detectingsystem 1 further includes an analyze device 14 and a clock generator 15.In some embodiments of the present disclosure, the analyze device 14 iscoupled to the comparing circuit 13 to receive the output signal OS viaan output pad P1. In some embodiments of the present disclosure, theanalyze device 14 includes a direct current (DC) meter to generate a CDFin response to the output signal OS and the reference voltage, andderive the noise level of the circuit to be detected or the OTA 111based on the CDF. In some embodiments of the present disclosure, theclock generator 15 is coupled to a comparator 8 (shown in FIG. 8) of thecomparing circuit 13 to provide a clock signal CLK via an output pad P2.In some embodiments of the present disclosure, a frequency of the clocksignal CLK is below 10 MHz.

In some embodiments of the present disclosure, the noise detectingcircuit 10 is integrated in an integrated circuit (IC). In someembodiments of the present disclosure, the noise detecting circuit 10 isformed on a semiconductor substrate of a wafer. In some embodiments ofthe present disclosure, the semiconductor substrate includes a pluralityof dies which are separated by scribe lines, and the circuit to bedetected and the noise detecting circuit 10 are disposed in the scribeline. It should be noted that the noise detecting system 1 may includeother essential elements/devices to achieve the basic function. Forexample, the noise detecting system 1 includes a DC supply device toprovide a supply voltage.

FIG. 2 is a diagram illustrating the amplifier circuit 11 in accordancewith an embodiment of the present disclosure. In some embodiments of thepresent disclosure, the amplifier circuit 11 includes am input terminalIN11, an output terminal OUT11, the OTA 111, and resistors R112 andR113.

In some embodiments of the present disclosure, the OTA 111 includesinput terminals Nin1 and Nin2 and an output terminal Nout1. In someembodiments of the present disclosure, the input terminal Nin1 is apositive input terminal of the OTA 111, and the input terminal Nin2 is anegative input terminal of the OTA 111. In some embodiments of thepresent disclosure, the input terminal Nin1 is coupled to a commonvoltage Vcm, and the input terminal Nin2 is coupled to the resistorsR112 and R113. In some embodiments of the present disclosure, the outputterminal Nout1 is coupled to the output terminal OUT11.

In some embodiments of the present disclosure, the resistor R112 iscoupled between the input terminal IN11 and the input terminal Nin2. Insome embodiments of the present disclosure, the resistor R113 is coupledbetween the output terminal OUT11 and the input terminal Nin2. Thoseskilled in the art should understand that the gain of the amplifiercircuit 11 is determined by R113/R112. In some embodiments of thepresent disclosure, the gain of the amplifier circuit 11 is about 30 dBto 45 dB.

FIG. 3 is a diagram illustrating the OTA 111 in accordance with anembodiment of the present disclosure. In some embodiments of the presentdisclosure, the OTA 111 includes transistors T21, T22 and T23 andresistors R21 and R22. In some embodiments of the present disclosure,each of the transistors T21, T22 and T23 is implemented by an N-typeMetal-Oxide-Semiconductor (NMOS).

In some embodiments of the present disclosure, a gate terminal thetransistor T21 is coupled to the input terminal Nin1, a drain terminalof the transistor T21 is couple to the resistor R21, and a sourceterminal of the transistor T21 is coupled to a drain terminal of thetransistor T23. In some embodiments of the present disclosure, a gateterminal the transistor T22 is coupled to the input terminal Nin2, adrain terminal of the transistor T22 is couple to the resistor R22, anda source terminal of the transistor T22 is coupled to the drain terminalof the transistor T23. In some embodiments of the present disclosure, agate terminal the transistor T23 is arranged to receive a bias voltageVbias, and a source terminal of the transistor T23 is coupled to theground. In some embodiments of the present disclosure, the resistors R21is coupled between a supply voltage and the transistor T21, and theresistor R22 is coupled between the supply voltage and the transistorT22.

The transistors T21 and T22 constitute an input pair, and the transistorT23 is configured to be a current source for providing a current throughthe transistor T23. However, the OTA 111 shown in FIG. 3 is only forillustrative purpose. Those skilled in the art should understand thatthe OTA 111 can be implemented by different architecture.

As mentioned above, the noise detecting system 1 proposed by the presentdisclosure is arranged to at least detect the noise level of the OTA 111or other circuits coupled to the OTA 111.

FIGS. 4A and 4B are diagrams illustrating the configurations of theamplifier circuit 11 for detecting the noise level of the OTA 111 inaccordance with an embodiment of the present disclosure. As shown inFIG. 4A, for detecting the noise level of the OTA 111, the inputterminal IN11 is coupled to a capacitor C11. The capacitor C11 isconfigured to be a DC block for stabling the alternate current (AC)ground. In some embodiments of the present disclosure, the capacitor C11can be an actual capacitor. In some embodiments of the presentdisclosure, the capacitor C11 can be implemented by coupling aGround-Signal-Ground (GSN) pad to the input terminal IN11. With suchconfigurations, the input signal IN is the noise of the OTA 111, whichis mostly from the input pair, and the circuit to be detected is the OTA111.

As shown in FIG. 4B, for detecting the noise level of the OTA 111, theinput terminal IN11 is coupled to a low dropout regulator (LDO) 5. TheLDO 5 is configured to be a DC block for stabling the AC ground. Withsuch configurations, the input signal IN is the noise of the OTA 111,which is mostly from the input pair, and the circuit to be detected isthe OTA 111.

FIG. 5 is a diagram illustrating the configurations of the amplifiercircuit 11 for detecting the circuit to be detected coupled to theamplifier circuit 11 in accordance with an embodiment of the presentdisclosure. As shown in FIG. 5, for detecting the noise level of thecircuit to be detected, the input terminal IN11 is coupled to thecircuit to be detected. With such configurations, the input signal IN isthe noise of the circuit to be detected and the noise of the OTA 111.

Those skilled in the art should readily understand, when there are aplurality of circuits to be detected, the noise detecting system 1 canfurther include a switching circuit including a plurality ofcorresponding switches, wherein each switch is coupled between a circuitto be detected and the input terminal IN11. By activating thecorresponding switch, the noise detecting system 1 can detect differentcircuit's noise level. The detailed architecture of the switchingcircuit is omitted here for brevity.

FIG. 6 is a diagram illustrating the filtering circuit 12 in accordancewith an embodiment of the present disclosure. In some embodiments of thepresent disclosure, the filtering circuit 12 includes an input terminalIN12, an output terminal OUT12, and filters 12_1, 12_2, . . . , and12_N, wherein N is a natural number. In some embodiments of the presentdisclosure, the filters 12_1, 12_2, . . . , and 12_N are coupled betweenthe input terminal IN12 and the output terminal OUT12. In someembodiments of the present disclosure, the input terminal IN12 iscoupled to the amplifier circuit 11, and the output terminal OUT12 iscoupled to the comparing circuit 13. The filter circuit 12 is arrangedto receive the amplified signal AS, and output the filtered signal FS byfiltering the amplified signal AS.

In FIG. 6, the filter 12_1 is shown for example to elaborate thedetailed architecture. In some embodiments of the present disclosure,the filter 12_1 includes a sub-output terminal Nout2, a resistor R31, acapacitor C31 and a switch SW31. In some embodiments of the presentdisclosure, a terminal of the resistor R31 is coupled to the inputterminal IN12 and another terminal of the resistor R31 is coupled to thesub-output terminal Nout2. In some embodiments of the presentdisclosure, a terminal of the capacitor C31 is coupled to the sub-outputterminal Nout2 and another terminal of the capacitor C31 is coupled tothe ground. In some embodiments of the present disclosure, a terminal ofthe switch SW31 is coupled to the sub-output terminal Nout2 and anotherterminal of the switch SW31 is coupled to the output terminal OUT12. Theswitch SW31 is arranged to selectively couple the sub-output terminalNout2 to the output terminal IN12. Those skilled in the art shouldunderstand the filter 12_2 to 12_N can also be implemented by thearchitecture shown in FIG. 6.

The resistor R31 and the capacitor C31 constitute a 1^(st) order lowpass filter. The corner frequency f0 of the filter 12_1 can berepresented as:

f10=1/(2*pi*RC),

wherein R is the resistance of the resistor R31, and C is thecapacitance of the capacitor C31. The corner frequency f0 means that thegain of the filter 12_1 is 20 dB decay after the corner frequency f0.Those skilled in the art should understand that the frequency responseof the filter 12_1 can be transformed into a brick wall profile, whereinthe brick wall frequency fx can be represented as:

fx=1/(4*R*C),

and brick wall frequency fx means that for any signal/noise received bythe filter 12_1, the signal/noise will be considered zero if thefrequency of the signal/noise is greater than the brick wall frequencyfx, which is better for the designer to estimate the actual magnitude ofthe signal/noise than the corner frequency f0. Those skilled in the artshould understand the brick wall frequency fx can be considered as thebandwidth of the filter.

In some embodiments of the present disclosure, the filter 12_1 to 12_Nare designed to have different bandwidth (i.e., different brick wallfrequency fx). By coupling the filters 12_1 to 12_N with the switch SW31therein to the comparing circuit 13 sequentially, the comparing circuit13 can thus output N samples of the output signal OS, which facilitatesthe estimate of the noise level of the circuit to be detected for thedesigner. The estimate of the noise level of the circuit to be detectedwill be discussed later.

Due to the process deviation, the actual resistance of the resistor R31and the actual capacitance of the capacitor C31 might be different fromthe simulation, and the deviation affects the actual brick wallfrequency and also the accuracy of the estimation. Therefore, in someembodiments of the present disclosure, the noise detecting system 1 canfurther include a calibration mechanism for calibrating the bandwidthcomposed by the resistor R31 and the capacitor C31 for each filter.

FIG. 7 is a diagram illustrating the calibration mechanism for theresistor R31 and the capacitor C31 in accordance with an embodiment ofthe present disclosure. In some embodiments of the present disclosure,the noise detecting system 1 further includes a buffer 7 coupled betweenthe switch SW31 of each filter and the analyze device 14. When thefilter 12_1 is tested, for example, the switch SW31 of the filter 12_1is switched to the buffer 7. By inputting a signal, which the magnitudeand the frequency are known, into the input terminal IN12 and observingthe frequency response shown on the analyze device 14, the actualresistance of the resistor R31 and the actual capacitance of thecapacitor C31 of the filter 12_1 can be deduced. Therefore, the actualbandwidth of the filter 12_1 can be learned.

FIG. 8 is a diagram illustrating the comparing circuit 13 in accordancewith an embodiment of the present disclosure. In some embodiments of thepresent disclosure, the comparing circuit 13 includes an input terminalIN13, an output terminal OUT13, and a comparator 8. In some embodimentsof the present disclosure, the input terminal IN13 is coupled to thefiltering circuit 12. In some embodiments of the present disclosure, theoutput terminal OUT13 is coupled to the output pad P1. The comparator 8is arranged to compare the filtered signal FS to the reference voltageVref, and output the output signal OS.

In some embodiments of the present disclosure, the comparator 8 includesinput terminals Nin3 and Nin4, and an output terminal Nout2. In someembodiments of the present disclosure, the input terminal Nin3 iscoupled to the reference voltage Vref. In some embodiments of thepresent disclosure, Nin4 is coupled to the input terminal IN13 toreceive the filtered signal FS. In some embodiments of the presentdisclosure, the output terminal Nout2 is coupled to the output terminalOUT13.

After being compared to the reference voltage Vref, the output signal OShas either a high voltage (i.e., a logic high value ‘1’) or a lowvoltage (i.e., logic low value ‘0’). However, in other embodiments ofthe present disclosure, the comparing circuit 13 can further includes avoltage-to-current converter, which is arranged to convert the outputsignal OS from the voltage form into a current form.

FIG. 9 is a diagram illustrating the noise after each circuit in thenoise detecting circuit 10 in accordance with an embodiment of thepresent disclosure. In the embodiment of FIG. 9, the noise detectingsystem 1 is configured to detect the noise level of the OTA 111, and theinput signal IN is the noise of the OTA 111, which is mostly from theinput pair.

After the amplifier circuit 11, the noise of the OTA 111 is amplified bythe gain of the amplifier circuit 11, and outputted as the amplifiedsignal AS, wherein the gain of the amplifier circuit 11 is determined byR113/R112. In some embodiments of the present disclosure, the gaindetermined by R113/R112 is about 30 dB to 45 dB. After the filteringcircuit 12, the noise of the OTA 111 as the filtered signal FS has 0.1to 0.2 dB loss due to the passive elements in the filtering circuit 12.In some embodiments of the present disclosure, the bandwidth of each ofthe filters 12_1 to 12_N in the filtering circuit 12 is designed to begreater than the frequency of the noise of the OTA 111 to prevent thenoise of the OTA 111 from being filtered by the filtering circuit 12.

After the comparing circuit 13, the noise of the OTA 111 is compared tothe reference voltage Vref and outputted as the output signal OS.Because the noise of the OTA 111 is amplified by the amplified circuit11, the noise level is thus much greater than the noise of thecomparator 8. Therefore, the noise of the comparator 8 does not affectthe estimation of the noise level of the OTA 11.

FIG. 10 is a diagram illustrating operations of the analyze device 14 inaccordance with an embodiment of the present disclosure. In operation1401, the analyze device 14 collects the logic values of the outputsignal OS in a predetermined time period in response to the referencevoltage Vref, and generates a CDF chart accordingly. As mentioned above,the filtering circuit 12 includes N filters 12_1 to 12_N havingdifferent bandwidth. Therefore, by sequentially coupling the filters12_1 to 12_N to the comparing circuit 13, the analyze device 14generates N CDF charts corresponding to N bandwidth.

For example, when the filter 12_1 is coupled to the comparing circuit 13and the reference voltage Vref is set, the output signal OS indicatingthe noise level of the OTA 111 is compared to the reference voltage Vrefin response to the bandwidth of the filter 12_1. After being compared tothe reference voltage Vref, the noise of the OTA 111 as the outputsignal OS is either logic high value ‘1’ or logic low value ‘0’.Therefore, in a predetermined time period, the analyze device 14collects those logic values of the output signal OS, and calculates thepossibility of the output signal OS being logic high value ‘1’ (or logiclow value ‘0’) in the predetermined time period. Next, the analyzedevice 14 adjusts the reference voltage Vref, and calculates thepossibility of the output signal OS being logic high value ‘1’ (or logiclow value ‘0’) again. By sweeping the reference voltage Vref, theanalyze device 14 generates a CDF chart of the output signal OS inresponse to the reference voltage Vref and the bandwidth of the filter12_1. Next, the filter 12_2 is coupled to the comparing circuit 13, andthe operation is executed again, and so on. Accordingly, N CDF charts ofthe output signal OS are generated.

In operation 1402, with the CDF charts of the output signal OS, theanalyze device 14 can derive the voltages, which indicate the noiselevel of the OTA 111, in response to the different bandwidth of thefilter 12_1 to 12_N. With the line chart obtained in the operation 1402,the designer can learn the noise level of the OTA 111, and also comparethe testing results to the simulation results. In operation 1403, theanalyze device 14 transforms the voltages into dB, and another linechart is obtained. By this, the slope of the flicker noise of the OTA111 can be learned from the slope of the line chart.

FIG. 11 is a flowchart illustrating a first part of a noise detectingmethod 100 in accordance with an embodiment of the present disclosure.Provided that the results are substantially the same, the operationsshown in FIG. 11 are not required to be executed in the exact order. Thefirst part of the method 100 is summarized as follows:

In operation 1001, a semiconductor substrate is provided. In someembodiments of the present disclosure, a plurality of circuitsconstituting a plurality of dies are formed on the semiconductorsubstrate, and separated by scribe lines thereon. In operation 1002, acircuit to be detected is formed in the scribe line. In some embodimentsof the present disclosure, the circuit to be detected can be a phaselock loop (PLL), a MOS, a bandgap, or an OTA. In operation 1003, aninput signal from the circuit to be detected is received, wherein theinput signal indicates a noise level of the circuit to be detected.

In operation 1004, an amplified signal is outputted by amplifying theinput signal. In some embodiments of the present disclosure, the inputsignal is received by an amplifier circuit (e.g., the amplifier circuit11). In some embodiments of the present disclosure, the amplifiercircuit includes an OTA (e.g., the OTA 111). In some embodiments of thepresent disclosure, the amplifier circuit amplifies the input signal bya predetermined gain (e.g., the gain decided by R113/R112). In someembodiments of the present disclosure, when the circuit to be detectedis the OTA, an input terminal (e.g., the input terminal IN11) of theamplifier circuit is coupled to a capacitor or a LDO as a DC block foestabling the AC ground, and the input signal is the noise of the OTA. Insome embodiments of the present disclosure, when the circuit to bedetected is other circuits than the OTA, the input terminal (e.g., theinput terminal IN11) of the amplifier circuit is coupled to the circuitto be detected, and the input signal is the noise of the circuit to bedetected and the noise of the OTA.

In operation 1005, a filtered signal is outputted by filtering theamplified signal. In some embodiments of the present disclosure, theamplified signal is received by a filtering circuit (e.g., the filteringcircuit 12). In some embodiments of the present disclosure, thefiltering circuit includes a plurality of filters having differentbandwidth. In some embodiments of the present disclosure, the bandwidthof the plurality of filters is greater than the frequency of the noiseof the circuit to be detected. In some embodiments of the presentdisclosure, each filter included in the filtering circuit includes a1^(st) RC filter, and the bandwidth of the filter can be represented as¼*R*C.

In operation 1006, an output signal indicating the noise level of thecircuit to be detected is outputted by comparing the filtered signal toa reference voltage. In some embodiments of the present disclosure, thefiltered signal is received by a comparing circuit (e.g., the comparingcircuit 13). In some embodiments of the present disclosure, thecomparing circuit includes a comparator (e.g., the comparator 8). Insome embodiments of the present disclosure, the comparator compares thefiltered signal to a reference voltage. In some embodiments of thepresent disclosure, the output signal has either logic high value ‘1’ orlogic low value ‘0’.

FIG. 12 is a flowchart illustrating a second part of the noise detectingmethod 100 in accordance with an embodiment of the present disclosure.Provided that the results are substantially the same, the operationsshown in FIG. 12 are not required to be executed in the exact order. Thesecond part of the method 100 is summarized as follows:

In operation 1007, a CDF in response to the output signal and thereference voltage is generated. In some embodiments of the presentdisclosure, the output signal is received by an analyze device (e.g.,the analyze device 14). In some embodiments of the present disclosure,when the filter is coupled to the comparing circuit and the referencevoltage is set, the analyze device 14 collects the logic values of theoutput signal, and calculates the possibility of the output signal beinglogic high value ‘1’ (or logic low value ‘0’). In some embodiments ofthe present disclosure, the analyze device 14 next adjusts the referencevoltage, and calculates the possibility of the output signal being logichigh value ‘1’ (or logic low value ‘0’) again. By sweeping the referencevoltage, the analyze device generate a CDF in response to the referencevoltage and the bandwidth of the filter.

In operation 1008, a voltage level, which corresponds to the noiselevel, in response to the bandwidth based on the CDF is derived.

According to an embodiment of the present disclosure, a noise detectingcircuit is disclosed. The noise detecting circuit includes an amplifiercircuit, a filtering circuit and a comparing circuit. The amplifiercircuit is arranged to amplify an input signal and output an amplifiedsignal, wherein the input signal is received from a circuit to bedetected and indicates a noise level of the circuit to be detected. Thefiltering circuit is coupled to the amplifier circuit and arranged tofilter the amplified signal and output a filtered signal. The comparingcircuit is coupled to the filtering circuit and arranged to compare thefiltered signal to a reference voltage and output an output signalindicating the noise level of the circuit to be detected.

According to an embodiment of the present disclosure, a noise detectingsystem is disclosed. The noise detecting system includes an amplifiercircuit, a filtering circuit, a comparing circuit and an analyze device.The amplifier circuit is arranged to amplify an input signal and outputan amplified signal, wherein the input signal is received from a circuitto be detected and indicates a noise level of the circuit to bedetected. The filtering circuit is coupled to the amplifier circuit andarranged to filter the amplified signal and output a filtered signal.The comparing circuit is coupled to the filtering circuit and arrangedto compare the filtered signal to a reference voltage and output anoutput signal indicating the noise level of the circuit to be detected.The analyze device is coupled to the comparing circuit via a firstoutput pad and arranged to generate a CDF in response to the outputsignal and the reference voltage.

According to an embodiment of the present disclosure, a noise detectingmethod is disclosed. The noise detecting method includes: providing asemiconductor substrate including a pluralities of circuits separated byscribe lines; forming a circuit to be detected in the scribe line;receiving an input signal from the circuit to be detected, wherein theinput signal indicates a noise level of the circuit to be detected;outputting an amplified signal by amplifying the input signal;outputting a filtered signal by filtering the amplified signal; andoutputting an output signal indicating the noise level of the circuit tobe detected by comparing the filtered signal to a reference voltage.

What is claimed is:
 1. A noise detecting circuit, comprising: anamplifier circuit, arranged to amplify an input signal and output anamplified signal, wherein the input signal is received from a circuit tobe detected and indicates a noise level of the circuit to be detected; afiltering circuit, coupled to the amplifier circuit and arranged tofilter the amplified signal and output a filtered signal; and acomparing circuit, coupled to the filtering circuit and arranged tocompare the filtered signal to a reference voltage and output an outputsignal indicating the noise level of the circuit to be detected.
 2. Thenoise detecting circuit of claim 1, wherein the amplifier circuitcomprises: an output terminal; an operational transconductance amplifier(OTA), connected to the output terminal; a first resistor, wherein aterminal of the first resistor is coupled to the output terminal, andanother terminal of the first resistor is coupled to an input terminalof the OTA; and a second resistor, wherein a terminal of the secondresistor is coupled to the input terminal of the OTA.
 3. The noisedetecting circuit of claim 2, wherein the amplifier circuit furthercomprises: a capacitor, coupled between another terminal of the secondresistor and a reference voltage source.
 4. The noise detecting circuitof claim 2, wherein the amplifier circuit comprises: a low dropoutregulator (LDO), coupled between another terminal of the second resistorand a reference voltage source.
 5. The noise detecting circuit of claim2, wherein another terminal of the second resistor is coupled to thecircuit to be detected.
 6. The noise detecting circuit of claim 1,wherein the filtering circuit comprises: an output terminal; and a firstfilter, selectively coupled to the output terminal, comprising: asub-output terminal; a switch, arranged to selectively couple thesub-output terminal to the output terminal; a resistor, wherein aterminal of the resistor is coupled to the amplifier circuit and anotherterminal of the resistor is coupled to the sub-output terminal; and acapacitor, wherein a terminal of the capacitor is coupled to thesub-output terminal and another terminal of the capacitor is coupled toa reference voltage source.
 7. The noise detecting circuit of claim 6,wherein the filtering circuit further comprises: a second filter,selectively coupled to the output terminal, wherein a corner frequencyof the first filter and a corner frequency of the second filter aredifferent.
 8. The noise detecting circuit of claim 6, furthercomprising: a switching circuit, arranged to selectively couple theoutput terminal to the comparator.
 9. The noise detecting circuit ofclaim 8, further comprising: a buffer, wherein the switching circuit isfurther arranged to selectively coupled the output terminal to thebuffer.
 10. The noise detecting circuit of claim 1, wherein thecomparing circuit comprises: a comparator, arranged to compare thefiltered signal to the reference voltage to output the output signal.11. The noise detecting circuit of claim 10, wherein the comparingcircuit comprises: a voltage-to-current converter, coupled to thecomparator and arranged to convert the output signal from a voltage forminto a current form.
 12. A noise detecting system, comprising: anamplifier circuit, arranged to amplify an input signal and output anamplified signal, wherein the input signal is received from a circuit tobe detected and indicates a noise level of the circuit to be detected; afiltering circuit, coupled to the amplifier circuit and arranged tofilter the amplified signal and output a filtered signal; a comparingcircuit, coupled to the filtering circuit and arranged to compare thefiltered signal to a reference voltage and output an output signalindicating the noise level of the circuit to be detected; and an analyzedevice, coupled to the comparing circuit via a first output pad andarranged to generate a CDF in response to the output signal and thereference voltage.
 13. The noise detecting system of claim 12, whereinthe amplifier circuit comprises: an output terminal; an operationaltransconductance amplifier (OTA), connected to the output terminal; afirst resistor, wherein a terminal of the first resistor is coupled tothe output terminal, and another terminal of the first resistor iscoupled to an input terminal of the OTA; and a second resistor, whereina terminal of the second resistor is coupled to the input terminal ofthe OTA.
 14. The noise detecting system of claim 13, further comprises:a switching circuit, comprising a plurality of switches, wherein eachswitch is coupled between a circuit to be detected and another terminalof the second resistor.
 15. The noise detecting system of claim 12,wherein the filtering circuit comprises: a plurality of filters, whereineach filter has different corner frequency and a corresponding switchfor selectively coupling the filter to the comparing circuit.
 16. Thenoise detecting system of claim 12, wherein the comparing circuitcomprises a comparator.
 17. The noise detecting system of claim 12,wherein the analyze device is further arranged to display a voltagelevel, which corresponds to the noise level, in response to the cornerfrequency based on the CDF.
 18. The noise detecting system of claim 12,further comprising: a clock generator, coupled to the comparing circuitvia a second output pad and arranged to provide a clock signal to thecomparing circuit.
 19. A noise detecting method, comprising: providing asemiconductor substrate including a pluralities of circuits separated byscribe lines; forming a circuit to be detected in the scribe line;receiving an input signal from the circuit to be detected, wherein theinput signal indicates a noise level of the circuit to be detected;outputting an amplified signal by amplifying the input signal;outputting a filtered signal by filtering the amplified signal; andoutputting an output signal indicating the noise level of the circuit tobe detected by comparing the filtered signal to a reference voltage. 20.The noise detecting method of claim 19, wherein the filtered signal isoutputted by a filter having a bandwidth, and the method furthercomprises: generating a CDF in response to the output signal and thereference voltage; and deriving a voltage level, which corresponds tothe noise level, in response to the bandwidth based on the CDF.